Technical Field
The present disclosure relates to a method for the surface treatment of a substrate of semiconductor material, in particular of a nozzle plate for ink-jet printers, and more specifically to a process for application of a chemically stable antiwetting coating confined on the surface of said nozzles.
Description of the Related Art
In numerous applications, it is necessary to apply a water-repellent and/or oil-repellent coating on surfaces exposed to liquids. In the case of ink-jet printheads, for example, it is necessary to apply an antiwetting coating (AWC) on the printing nozzle plate to prevent formation of ink residue during and after ink-jet printing. In fact, the accumulation of residue around the orifice of the nozzle from which the drops of ink are expelled may alter the direction of the drop, thus causing a degradation of the quality of the printed images.
The antiwetting treatment must further be applied only on the outside the orifice of the nozzles to prevent the printing resolution from being affected and must be chemically stable if it is arranged in contact with acidic or basic solutions, as are many water-based inks, which would otherwise destroy the AWC in a short time.
The antiwetting treatment of surfaces such as silicon, glass, or other inorganic or organic substrates, may be obtained by depositing an antiwetting polymeric layer by lamination, spin coating, or chemical vapor deposition (CVD).
These treatments may offer good surface properties and excellent chemical stability, but are frequently unstable to delamination from the substrate when they are arranged in contact with the liquids. This phenomenon is due to the weak interaction of a physical type that binds together the deposited layer and the substrate. These physical interactions are in general due to hydrogen bonds or Van der Waals forces. Further, these deposition techniques may cause the AWC to be applied inside the orifice of the nozzle, thus causing alteration of the printing process.
Alternatively, an antiwetting treatment may be obtained through a coating of a chemical type by creating chemical bonds, which are stronger than physical bonds. Typically, this coating is obtained with the use of molecules such as alkyl silanes, perfuoro alkylsilanes, chlorosilanes, or alkoxy silanes.
On the silicon surfaces, for example, alkyl silanes form a uniform monolayer (with a thickness ranging from a few Angstrom to hundreds of nanometers) chemically bound to the silicon surface through a Si—O—Si bond.
The above coatings are not subject to delamination and make it possible to obtain the desired surface properties through an appropriate choice of the alkyl tail. This type of coating is, however, known to be unstable when exposed to aqueous environments, as many water-based inks. In particular, the Si—O—Si anchorage bonds are unstable in aqueous environments, above all if at a non-neutral pH.